Roller Versus Centrifugal Pumps

John Ingram BS CCP

• What is the Ideal/Optimal Pump
• Roller Pumps
  • How they Work
  • The Proper Occlusion Techniques
  • Advantages and Disadvantages
• Centrifugal Pumps
  • How they Work
  • Advantages and Disadvantages
• Studies

Optimal Blood Pump

• Tayama et al. Suggested That the Ideal Blood Pump for ECC Must:
• Have the Capacity to Deliver up to 7 l/min Against a Pressure of 500 mm Hg
• Should not Damage the Cellular or Acellular Components of the Blood
• Should Have Smooth Surfaces
• Must be Free of Areas of Stasis or Turbulence
• Should Have Accurate and Reproducible Flow Measurement
• Should Have a Back-up or Manual Mode of Operation in Case of Motor Failure

Roller Pumps – How They Work

The Propulsion of Blood Occurs by the Action of Two Rollers Sequentially Compressing a Segment of Tubing Causing the Forward Movement of Blood

Roller Pumps – Proper Occlusion

• PRESSURE METHOD  (can be done with sterile circuit primed)
• Place Fluid Primed Tubing Inside Roller Head
• Must Have a Pressure Manometer Integrated into the Positive Flow Outflow Line
• Tighten Occlusion of the Pump until Fully Occluded
• Clamp Outflow Line Immediately Beyond the Pressure Manometer
• Manually Rotate Pump Head until Manometer Reads 200 mmHg
• Slowly Back off the Occlusion until the Pressure Drops to 100 mmHg Over 1 Minute
• Do the Same for the Other Roller on the Pump

Roller Pumps – Proper Occlusion

• WATER COLUMN METHOD (can not be done sterile)
• Place Tubing Inside Roller Head
• Must Have a Bucket of Water with Inflow Outflow Lines under Water
• Circulate the Water to Prime the Lines
• Tighten Occlusion of the Pump unti Fully Occluded
• Hold Outflow Line Vertical with ends two Feet Above the Pump Head
• Slowly Back off the Occlusion until the Fluid Level Drops 1 mm/min
• Do the Same for the Other Roller on the Pump

Roller Pumps Advantages:

• Less Expensive
• Lower Prime Volume
• Easy to Prime
• Flow is not After Load Dependent *
• Reliable Constant Flow Rate
• Do Not Allow Retrograde Flow

Roller Pumps Disadvantages:

• Occlusive
• Are Not After Load Dependent
• Will Pump Against any Resistance and may Result in Vessel
  Dissection, Pump Tubing Disconnection or Rupture
• Capable of Pumping Massive air Through the Outflow   Line

Preload Dependent

• Highly Capable of Cavitation
• As the Tubing Expands Behind the Roller, There is a Period of Negative Pressure
• This Momentary Negative Pressure in the Absence of Adequate Preload, May   Induce The Cavitation Of Air Dissolved In The Solution

Hemolysis

• The Magnitude of Hemolysis is Related to both the Time and Exposure of the   Blood to Shear Forces Generated by the Pump
• A Region of High Pressure and Shear Force is Created at the Leading Edge of the   Roller Where the Tubing is Compressed
• Over Occlusion:  Crushes the Cellular Components Causing Hemolysis
• Under Occlusion:  Causes Severe Forward and Backward Turbulence Causing
  Shear Stress and Hemolysis

Spallation

• Particulate Emboli may be Generated by Micro Fragmentation (or Spallation) of the Inner Surface of the Tubing where the Roller Contacts the Tubing and where the Fold at the Edges of the Tubing Occurs
• Studies of Tubing wear over Time have shown that Polyvinylchloride Fragments Generated from Roller Pumps are Numerous, Frequently 20 mm in Diameter, and begin to Occur During the First Hour of use

Centrifugal Pumps – How They Work

• Are Nonocclusive Pumps that Function by Producing a Constrained Vortex Within a   Polycarbonate Structure
• The Inner Mechanism may Either be Cones or Impellers that Rotate at a High RPM
• The High RPM Exerts an Outward Centrifugal Force on the Blood where the Outlet is   Located,  Where it Exits the Pump and Results in Forward Movement of Fluid
• Blood Flow Rate is Increased by Increasing the Revolutions per Minute Thereby   Increasing the Centrifugal Force Exerted
• The Disposable Pump Head is Coupled to the Console Unit via Magnetic Motor Drive

Centrifugal Pumps Advantages

• Non – Occlusive, will not Pump Against any Resistance
• Are After Load Dependent
• Less likely to Result in Vessel Dissection, Pump Tubing             Disconnection or Rupture
• Flow is Preload Dependent
• No Cavitation
• Less Hemolysis
• Will De-Prime when challenged with Gross Air

Centrifugal Pumps Disadvantages

• More Expensive
• Increased Prime Volume
• More Difficult to Prime
• Allow for Retrograde Flow
• Less Likely to Result in Vessel Dissection, Tubing Rupture or    Disconnection
• Thrombus formation  Low Anticoagulation / Long Pump Runs
• Heat Generation (Hemolysis, Clotting)
• Magnetic Decoupling

Research Studies:

A Number of Investigators have Performed in vitro Studies Comparing Centrifugal   Pumps and Roller Pumps in Terms of Blood Handling During Short & Long-   Term use

Tamari et al. Examined Hemolysis under Various Flow and Pressure Conditions in   vitro using Porcine Blood and Concluded that the Hemolysis was Related to:

Duration of Blood Exposure to Shear Stress

The Pump Pressure of the Outflow

The Flow Rate of the Pump

Many Studies Reported Less Hemolysis with Centrifugal Pump When Tested in Vitro

Many Trials have been Conducted to Compare Centrifugal and Roller Pumps in Relation to Emboli Generation, Blood Trauma, and Clinical Outcomes

In a Randomized Trial by Wheeldon et al., Found Centrifugal Pump to Have

Significantly Less Micro-emboli Generation

Less Complement Activation

Better Preservation of Platelet Count was Observed in Patients with Centrifugal   Pump

Many Trials have been Conducted to Compare Centrifugal and Roller Pumps in Relation to Emboli Generation, Blood Trauma, and Clinical Outcomes

In a Randomized Trial by Wheeldon et al., Found Centrifugal Pump to Have

Significantly Less Micro-emboli Generation

Less Complement Activation

Better Preservation of Platelet Count was Observed in Patients with Centrifugal   Pump

Literature:

Bharat Datt, MSc, CCP, CPC, FPP; Moui B. Nguyen, CCP; Gary Plancher, CCP; Mark Ruzmetov, MD, PhD, SA-C; Michael O’Brien, PA-C; Alicia Kube, RN; Hamish M. Munro, MD, FRCA; Kamal K. Pourmoghadam, MD; William M. DeCampli, MD, PhD

The Impact of Roller Pump vs. Centrifugal Pump on Homologous Blood Transfusion in Pediatric Cardiac Surgery
J Extra Corpor Technol. 2017;49:36–43 The Journal of ExtraCorporeal Technology
The Heart Center at Arnold Palmer Hospital for Children, Orlando, Florida
Presented at the 53rd AMSECT International Conference, Tampa, Florida, April 17 2015 and the Society for Advancement of Blood Management 2015 Annual Meeting
240 Pediatric Patients
140 Centrifugal Pump and 100 Roller Pump
Roller Pump Group
Decreased Priming Volume
Increased Hct Blood Primes
Decrease in Intra-Operative Transfusions
Decreased Mortality
Research Studies – Closing Comments

In researching the clinical benefits of one type of pump versus the other, in terms of  hemolysis, inflammatory response (cytokines, complement, interleukins), fibrinolysis, platelet activation, etc., one is likely to discover many contradicting studies.  There are likely as many studies claiming one type of pump over the other, in many short term and long term clinical aspects.  For example there are studies demonstrating centrifugal pumps being more gentle (less hemolytic, etc.), however there are studies that conclude that even a poorly occlusive roller pump is less hemolytic than centrifugal pumps.  There are many studies that have found no clinical difference in outcomes.

In the end, it remains the education of the perfusionist to research and conclude for one’s self which is best for their patients.  However, there is one stand out characteristic that centrifugal pumps have above roller pumps, and that is in the area of Safety.